1. Field of the Invention
The present invention relates to an exposure apparatus and a device manufacturing method.
2. Description of the Related Art
A process of manufacturing a semiconductor device formed from an extra fine pattern has conventionally adopted a reduction projection exposure apparatus which reduces and projects, on a substrate such as a wafer coated with a photoresist, a circuit pattern drawn on a reticle (mask), thereby exposing the substrate. Along with an improvement in the packaging density of semiconductor devices, further micropatterning of a circuit pattern is required, and an exposure apparatus which can uniform the finishing size (line width) of a pattern is desired.
A conventional exposure apparatus exposes a photoresist coated on a substrate with an exposure amount (dose) corresponding to the photoresist. An exposure apparatus adopting the step-and-repeat scheme repeatedly performs an exposure with a given exposure amount while moving in a shot region on a substrate. Even if, however, the exposure apparatus repeatedly exposes a photoresist with a given exposure amount in each shot within a substrate plane, there is a difference (pattern line width error) between the line width of the obtained pattern and that of a designed pattern. To maintain the line width uniformity of a pattern, various exposure methods of correcting an exposure amount depending on a shot have been disclosed. For example, Japanese Patent Laid-Open No. 2005-197362 discloses a method of controlling, as an nth-order polynomial function, an exposure amount at a position in each shot on a substrate plane. Furthermore, Japanese Patent Laid-Open No. 7-29810 discloses a method of controlling an exposure amount according to the distance from the center position on a substrate plane.
The conventional techniques adjust an exposure amount within the substrate plane but do not adjust an exposure amount for uniforming a line width distribution within a shot region, thereby disabling precise adjustment of a pattern line width error within each shot region.